Procedures for olfactory conditioning in crickets. (A) For appetitive or aversive conditioning, an odor (e.g., apple or banana odor) was paired with water (appetitive US) or 20% sodium chloride solution (aversive US). A syringe containing water or sodium chloride solution was used for US delivery. A filter paper soaked with apple or banana essence was attached to the needle of the syringe. The filter paper was approached to the cricket’s antennae, and then water or sodium chloride solution was presented to the mouth. (B) Apparatus for the odor preference test. Two holes (H) connecting the chamber with odor sources (OS) were inserted in the floor of the test chamber (TCH). Each odor source consisted of a container with a filter paper soaked with apple or banana essence, covered with a fine gauze net (N). Three containers were mounted on a rotating container holder (CH), and two of three odor sources could be presented at the same time. A cricket was placed in the waiting chamber (WCH) for 4 min for acclimation and then allowed to enter the test chamber to visit odor sources, by opening a sliding door (SD). Two minutes later, the relative positions of the apple and banana sources were changed. The preference test lasted for 4 min. RA: rotating axle. Modified from Matsumoto and Mizunami .